Now create cur,new,tmp in '.' even if existsok is false

Otherwise, there was a race where sometimes subfolders would get created
first in the sep = '.' scneario

fixes OfflineIMAP#64

offlineimap/repository/Maildir.py

@@ -87,7 +87,7 @@ def makefolder(self, foldername):
         # makedirs will fail because the higher-up dir already exists.
         # So, check to see if this is indeed the case.
 
-        if (self.getsep() == '/' or self.getconfboolean('existsok', 0)) \
+        if (self.getsep() == '/' or self.getconfboolean('existsok', 0) or foldername == '.') \
             and os.path.isdir(foldername):
             self.debug("makefolder: %s already is a directory" % foldername)
             # Already exists.  Sanity-check that it's not a Maildir.